live - 60fps 1920 x 1080
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Glowing Fireflies</title>
<style>
body {
margin: 0;
overflow: hidden;
background-color: #020617;
/* Very dark slate */
/* Add some depth to the night sky */
background-image: radial-gradient(circle at 50% 100%, #0f172a 0%, #020617 80%);
}
canvas {
display: block;
width: 100vw;
height: 100vh;
}
</style>
</head>
<body>
<canvas id="fireflyCanvas"></canvas>
<script>
const canvas = document.getElementById('fireflyCanvas');
const ctx = canvas.getContext('2d');
let width, height;
let fireflies = [];
const config = {
count: 150,
color: '#d9f99d', // Lime/yellow glow
sizeMin: 1,
sizeMax: 2.5,
speed: 0.5,
wander: 0.2 // How erratic they move (Brownian motion)
};
function resize() {
width = canvas.width = window.innerWidth;
height = canvas.height = window.innerHeight;
}
class Firefly {
constructor() {
this.x = Math.random() * width;
this.y = Math.random() * height;
this.vx = (Math.random() - 0.5) * config.speed;
this.vy = (Math.random() - 0.5) * config.speed;
this.baseSize = config.sizeMin + Math.random() * (config.sizeMax - config.sizeMin);
// For pulsing glow
this.angle = Math.random() * Math.PI * 2;
this.pulseSpeed = 0.02 + Math.random() * 0.03;
// For organic drifting
this.wanderAngle = Math.random() * Math.PI * 2;
}
update() {
// Organic erratic drifting (Brownian motion)
this.wanderAngle += (Math.random() - 0.5) * 0.5;
this.vx += Math.cos(this.wanderAngle) * config.wander * 0.1;
this.vy += Math.sin(this.wanderAngle) * config.wander * 0.1;
// Speed limits
const currentSpeed = Math.sqrt(this.vx * this.vx + this.vy * this.vy);
if (currentSpeed > config.speed * 2) {
this.vx = (this.vx / currentSpeed) * config.speed * 2;
this.vy = (this.vy / currentSpeed) * config.speed * 2;
}
this.x += this.vx;
this.y += this.vy;
// Screen wrapping
if (this.x < 0) this.x = width;
if (this.x > width) this.x = 0;
if (this.y < 0) this.y = height;
if (this.y > height) this.y = 0;
// Update pulsing
this.angle += this.pulseSpeed;
}
draw() {
// Calculate opacity using sine wave for smooth throbbing glow
const alpha = (Math.sin(this.angle) * 0.5 + 0.5) * 0.8 + 0.1;
const size = this.baseSize;
// Core
ctx.beginPath();
ctx.arc(this.x, this.y, size, 0, Math.PI * 2);
ctx.fillStyle = `rgba(217, 249, 157, ${alpha})`;
ctx.fill();
// Diffuse Glow
if (alpha > 0.4) {
ctx.beginPath();
const gradient = ctx.createRadialGradient(this.x, this.y, size, this.x, this.y, size * 6);
gradient.addColorStop(0, `rgba(163, 230, 53, ${alpha * 0.5})`);
gradient.addColorStop(1, 'rgba(163, 230, 53, 0)');
ctx.fillStyle = gradient;
ctx.arc(this.x, this.y, size * 6, 0, Math.PI * 2);
ctx.fill();
}
}
}
function init() {
resize();
fireflies = [];
let c = window.innerWidth < 768 ? Math.floor(config.count / 2) : config.count;
for (let i = 0; i < c; i++) {
fireflies.push(new Firefly());
}
}
function animate() {
ctx.clearRect(0, 0, width, height);
// Optional: Draw some ambient foreground elements or background trees here
// Draw fireflies
ctx.globalCompositeOperation = 'screen';
for (let i = 0; i < fireflies.length; i++) {
fireflies[i].update();
fireflies[i].draw();
}
ctx.globalCompositeOperation = 'source-over';
requestAnimationFrame(animate);
}
window.addEventListener('resize', init);
init();
animate();
</script>
</body>
</html>About this animation
Jittery, bioluminescent canvas particles that drift organically through a dark foreground.
Under the hood
Brownian Motion Sub-Routines
To make these fireflies look like living organisms rather than rigid code, they employ Brownian Motion. The velocity vector incorporates a 'wander angle' that shifts randomly every single frame (
Math.sin(this.wanderAngle)). This prevents them from moving in straight lines, simulating erratic, organic flight. 
